1. Field of the Invention
The present invention relates to a semiconductor optical device.
2. Related Background Art
Semiconductor lasers are known in which an active layer made of GaInNAs is provided on a GaAs substrate, and a diffraction grating is formed in which convex sections and concave sections are periodically arranged on this active layer (see Laid-open Japanese Patent Application No. H11-74607 and Laid-open Japanese Patent Application No. 2003-202529).